Electric organ



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ELECTRIC ORGAN Filed June 12. 1937 9 Sheets-Sheet 8 n; E Lm/w/va DRIVE/V PHO/V/C Fkfwffims FREQ M g g 0 cr w k E 654: GEAR WHEEL 1: 3 5 as q BRA 5 B'Mfl/TE GE/lf/MTL'DGEWERATfD g E g k 2 w b 5 Wt kSBYCf/ORMSBYGOLO Q l g 3*$ 6 W Q 5 o :3 c Q 6544347015 GLWERATOI? C) 3 o v a, a w 2 k m z w w u n: t i u 1 6 66 101 57 121 92 56d 63 780.662 784000 3.346 .1010: .91 121a 74 56b 32 7874026 +305 9.9 82 7.273 2.99 7 833.684 830270 +3.4l4 8 76.622 3. 47:51 882.758 +2. 758 .92 8. 421 a. 752 936.296 f +412 9 88.836 3.693 991.548 987928 +4120 1042.222 3.931

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ELECTRIC ORGAN Filed June 12, 1937 9 Sheets-Sheet 9 1120110 1020 07 000 4202900 +10094 1070120 1270 09 000127 441 .414 1070120 1270 09 000120 4402174 4440000 +12174 10 o 87 201 0 1220 07 070127 4070.947 4 04000 -20003 1020100 1220 07 070120 4 10709 7 V 4-11.709 88 1090121 1290 62 000127 4907097 4981 f -24020 1090121 1290 02 000 120 4990129 +14007 1040120 1240 00 090127 02001 2- -24020 1040120 1240 00 090 120 0290.002 5280000 +10.052 1110100 1010 47 900127 0000.000 -20.001 1110100 1010 47 900120 5610.213 5693044 4-17169 91 1000100 1200 00 910127 0090.420 5 2 20.140 1000100 1200 00 910120 094200 4571 4-10.200 0: a ER EE Q g E E E Q {g w t, o g FREQl/f/VC/[S FREQUENCY g Q g u "J 6 m fig 2 L gr. 2 5 E ii GENERATED GENERATED 3 5%; k n 2 g 0 IV/NG 0 NE HON c BYCHOR BY 60w Q ik EAR EAR WHEE Q m E g B A66 PM E GfA/ERATORS 6000mm)? Q m B U I u I k .L 11m 12 YE: 3211 1211 lxfidzwtor (X 7% zawi'ezwjfzrmmvd Patented May 23, 1939 UNITED STATES PATENT OFFICE 11 Claims.

My invention relates to improvements in electrical musical instruments generally, and more particularly to improvements in electric organs of the type described in detail in my United States Patent No. 1,956,350. 7

Electric organs, as described above, are now manufactured in large numbers and have achieved popularity owing to their ability to synthesize a wide variety of tone colors, and to produce a wide range of different musical effects from a single series of electric generators. each one of which produces one of the fundamental pitches of the tempered musical scale. By the present invention it is possible to extend the variety of musical eflects which may be produced by the addition of other apparatus which cooperates eflectively with the system above described.

The object of the invention is therefore to extend and improve the variety of musical effects which may be obtained from these instruments.

Further objects will appear from the following description, reference being had to the accompanying drawings, in which:

Figures 1, 1a, lb together constitutes a horizontal sectional view of the chorus generator assembly;

Figure 2 is a transverse sectional view of the generator assembly taken on the line 2-2 of Figure la;

Figure 3 is a plan view, partly in section, showing the top of the chorus generator assembly and the gang switch assembly;

Figure 4 is a vertical sectional view taken on the line 4-4 of Figure 3;

Figure 5 is a fragmentary sectional view taken on the line 5-5 of Figure 4;

Figure 6 is a side elevational view of the gang switch operating mechanism;

Figure 7 is a view similar to Figure 8, on a reduced scale, showing the parts in switch opening position;

Figure 8 is a perspective view of one of the switches and its operating member;

Figure 9 is a wiring diagram showing representative parts of the complete instrument; and

Figures 10 and 10a together constitute a chart showing the characteristics of the individual generators and their driving means.

GENERAL Dascnir'rron The detailed description oi the instrument of my invention will be more readily understood if it is read with a previous general knowledge of the function and operation of the instrument as a whole. The following description is intended to furnish such general understanding of the invention.

The more simple type of organ on which this invention is an improvement comprises, in general, a bank of mechanical generators of alternating current, manuals of keys and a pedal clavier, all of which operate to close switches whereby electric currents generated by the various generators are allowed to pass into a common output circuit. The circuit produces an electric signal which is usually amplified by vacuum tube amplifiers and made audible by some form of loud speaker. The instrument is capable of producing many different types of tone quality because of the fact that complex tones are synthesized from different harmonically related frequencies produced by different generators.

When a single key of the manual is depressed a multiple contact switch is closed. In the common form of this instrument, the switch under each key closes nine separate circuits. Each circuit connects the output of one of the generators to one of nine bus bars. The bus bars pass through the various key switches and conduct the current from the generators to various taps on a common output transformer. By connecting the various bus bars to different taps on the transformer it is possible to regulate the relative amounts of energy delivered to the output circuit by the bus bar circuits.

It is a well known fact that the tone quality of a single sustained musical note is determined by the relative amounts of energy of different frequencies which are related to one another as the so-called harmonic series. If, for instance, the fundamental pitch of a musical note of the scale such as A is 440 cycles, then this note may contaln other frequencies which are related to the fundamental as whole multiples. The second harmonic, for instance, is the frequency 880 which is musically the pitch of a note one octave higher in the scale, and is therefore also an A. The third harmonic is the frequency three times 440, or 1320. The fourth harmonic is 1760 and so on. The various frequencies for the harmonic series are supplied from different generators, each of which is tuned to the fundamental pitch of a note of the musical scale, each frequency being related to its predecessor in the ratio of the twelfth root of two as closely as this relationship may be obtained by gearing. In the common form of instrument, there are 91 generators.

If any generator in the lower range of frequency is employed to produce the fundamental pitch, then other generators will be found producing frequencies which are exactly twice, four times, eight times, and sixteen times greater. Generators will also be found which are not exactly but are very closely related to the fundamental frequency for the third, sixth and twelfth harmonics. Relationships in this case, while they are not exact, are in error by, roughly, one part in a thousand and the diiference between the harmonic which is thus "borrowed" from the tempered musical scale and the "natural" harmonic obtained by multiplying the fundamental frequency by three, six or twelve is a difference which is so slight that the ear cannot detect It.

I have made a number of laboratory experiments in which a complex note was synthesized from currents produced from separate sources. In such experiments it is possible so to arrange the apparatus that a switch will alternately connect in a harmonic which is borrowed from the tempered scale or which is an "exact" harmonic from a separate source. Throwing the switch either way makes no difference in the quality of a single complex note. We may therefore say that the two systems are equivalent in the musical quality of the sound produced, provided that one or the other is used separately. There is, of course, a difference if some of both frequencies are present because the ear can then detect them through the phenomenon of beats. The frequencies differing from each other by one part in a thousand will produce a relatively slow beat when the frequencies are quite high.

Similarly, a generator will be found which produces a frequency which is very close to the fifth harmonic of a lower frequency of the series. In this case, however, the difference is somewhat larger, being of the order of about one part in 250. This difference is enough to be perceptible in some parts of the scale for some people as the average musician is capable of discerning a difference in pitch of the order or one part in 300 in the middle range of frequencies. That is to say he can detect such a difference when listening critically to one frequency sounded alone followed immediately by another frequency which diflers from it by approximately one part in 300. I have not, however, found any one who could detect any difference in quality of a note of a complex nature in which no change was made other than the substitution of the "borrowed" from the "natural fifth harmonic. It is possible that such persons exist but they must be very uncommon.

In these organs, as they have been made heretofore, no beats of any kind are normally heard in playing complex chords, each note of which is represented by a complex series of frequencies. This is due to the fact that the same frequency is used, for example, for the third harmonic of a certain note as is used for the second harmonic of a different note of the chord. The same generator is employed to deliver an amount of current necessary to reproduce the sum of the effects necessary to represent the third harmonic of one note and the second harmonic of another.

ingly desirable, but this system does not permit other effects which have heretofore been assoclated with certain other instruments and choruses of instruments.

The pipe organ, for instance, derives certain effects which are commonly associated with the "full organ tone. In this case the sound of the whole is made up by a chorus of a large number of different pipes. Among so many pipes there are a great many which are not in exact tune with one another. Experience has shown that the amount by which they are likely to be oil tune from one another is no small amount when it is compared with the order of difference which we have been discussing in connection with "borrowed" and "natural" harmonics. It is owing to these differences in tuning that the full organ, and the violin section of a symphony orchestra, for instance, produce an effect which may be best characterized as a chorus. when, for example, a number of violinists play together they naturally make an attempt to play on key with one another. Even assuming that the technique of each violinist was perfect, they would, nevertheless, not play exactly in unison because no one of them could detect a difference which was no larger, for instance, than one part in 300. Actually, of course, they are likely to be off key from one another by more than this amount because that is the maximum accuracy which they could hope to develop and some are likely to be more flat or sharp than they could actually recognize in a simple critical test.

There is therefore an intrinsic difference between the sound produced by a number of violins playing in unison and the sound of one violin being played more loudly. It has been the experience of symphony orchestra conductors that apart from an increase in loudness there is a certain desirable-richness of tone produced by the ensemble playing of a group of first violins. One prominent conductor stated that in his opinion and experience the richness increased with additional violins up to a number which he roughly placed at twenty. Adding more violins thereafter, in his opinion, merely increased the volume. If as many as twenty violinists play in unison, there must be a statistical average of off pitch frequencies which does not materially increase with more instruments.

By the present invention I have found a means of combining relatively simple apparatus with the existing type of electric organ whereby it is possible to add the so-called "chorus effect by the addition of other generators which produce frequencies which are intentionally of! pitch by certain amounts.

Generator assembly Referring to Figures 1, 1a, lb, and 2, the chorus generator assembly comprises a plurality of vertical transverse frame plates I and vertical longitudinal frame plates I52 and I54. Each of the frame plates has a pair of lugs I56 which project through suitable apertures in the longitudinal frame plates I52, I54, respectively, whereby the frame plates I50 are properly spaced. As additional means for accurately spacing the frame plates I50, longitudinally extending bars I58, I60, and I62 are provided.

These bars I50 are provided with notches I which register with the vertical frame plates I50 and are held in interlocking engagement therewith by'a pair of wires I85. A pair of rods I88, I18 extend the full length of the assembly and make the assembly more rigid.

As is best shown in Figures 2, 4, 5 the phonic wheel generators each comprise a phonic wheel 81b (Figure 4) which is staked to a suitable hub I12 which is secured to a shaft I14. (There are present in the complete assembly 12 phonic wheel designated 88a and 88b to 8Ia and 8ib.) The shaft I14 is mounted for free rotation in a pair of composition bearings I11 carried in the vertical frame plates I88. In some instances. as is shown in Figure 4, there'may be two phonic wheel rotors as Ma. and lib staked to a single hub I12. A driven gear I28a is mounted for free rotation upon the shaft I14 and is adapted to drive the phonic wheel generator assembly through a pair of compression and torsion coil springs I18. The ends of the springs I18 are bent back upon themselves as indicated in Figure 4 and are thus free to move relative to the phonic wheels 81b and 8Ib, as well as with respect to the driven pinion I28a. By this type of driving connection the phonic wheels are elastically and frictionally driven.

All of the generators are driven by a suitable synchronous motor connected to a sectional countershaft I18, the various sections of which are mounted in suitable bearings in the vertical frame plates I88 and are connected together by articulation plates I88. The countershaft sections I18 carry a pluraiity'of driving gears I8ia to II2a as shown in Figures 1, la, and lb, The driving connection from the synchronous motor to the first countershaft is shown in Figure 1 as including a relatively long helical torsion spring I82 and other parts of the construction described in my prior Patent No. 1,956,350.

The synchronous motor used to drive the generator assembly is of a non-self-starting type and an additional starting motor I88 (Figure lb) is therefore provided to launch the synchronous motor. This motor may be of the induction type and has a driving pinion I88 connected to its rotating armature, this pinion being adapted to mesh with a gear I88. When current is supplied to the motor its armature shifts axially and the pinion I88 is meshed with a gear I88 mounted upon the countershaft section I18 at the left end of the generator assembly. The gear I88 transmits rotary motion to the shaft section I18 through a suitable spring driving connection. The pinion I88 is disengaged from the gear I88, when the motor I88 is no longer energized, by means of a leaf spring I82 which presses against the end of the armature shaft of the motor. Thus the motor I88 will, when connected to a suitable source of current, cause its pinion I88 to engage the gear I88 and rapidly accelerate the generator assembly and the synchronous motor connected thereto to a speed slightly above its synchronous speed. As soon as this speed is attained, the starting motor I88 may be de-energized, whereupon its pinion will slide out of engagement from the gear I98. Suitable switches, usually operated manually, are provided to control the supply of current to the starting motor I88 and to the synchronous motor.

Adjacent each of the phonic wheel rotors 88a to 8) is mounted a permanent magnet I82 (Figure 2), each of the magnets having a wedgeshaped point I84 located in close proximity to the phonic wheel rotor. The air gap between the rotor and the point I84 may be varied by adjustment of the magnet in its mounting bushing I88, and its correct position fixed by means of a set screw I88. Each of the magnets I82 has a coil 288 mounted thereon adjacent its point I84. One terminal of each of these coils 288 is grounded while the other is connected by a suitable conductor 282 with a soldering lug 284 riveted to an insulating strip 288 which in turn is secured to the top plate 288 of the generator assembly.

Gang switch assembly The gang switch assembly, whereby the various generators may be optionally connected to and disconnected from controlling key switches. comprises a plate 2i 8 which is supported from the cover plate 288 by a plurality of studs 2I2. A plurality of resilient switch fingers 2 are secured to a strip 2I8 of insulating material extending beneath the plate 2I8 and mounted in spaced relation relative thereto by the studs 2I2, and additional bolts. Movable switch fingers 2I8 are mounted upon an insulating strip 228 similar to the strip 2I8, and similarly carried by the studs 2i 2 and top plate 2I8. The switch fingers 2i 8 are secured to the insulating strip 228 by means of rivets 22I which also serve to hold soldering lugs 222 in electrical contact with the respective switch fingers 2I8. Each of the switch fingers 2 has a short length of contact wire 224 welded thereto, while the cooperating switch finger 2I8 has a similar short length of contact wire 228 welded thereto so as to lie substantially perpendicular to the contact wire 224.

A switch operating shaft 228 is mounted for rotation in a plurality of bearings 288 secured to the top plate 2I8. The shaft 228 has a keyway 232 cut therein to receive an insulating strip 234 which forms an actuator for the switch fingers 2I8. When the shaft is rotated counterclockwise, from the position in which it is shown in Figure 2, through an angle of slightly less than degrees, the edge of the insulating strip 234 engages the switch fingers 2I8 and raises them sufficiently to separate their contact wires 228 from the cooperating contact wires 224. The switch fingers 2 and 2I8 are made of thin flexible metal, such as phosphor bronze, and as a result the switch fingers 2 will fiex slightly when the contact is made, due to the resilient pressure of the associated spring finger 2I8. There will thus be a slight wiping action between the contact wires 224 and 228, which will assure the making of good electrical contacts.

The shaft 228 is actuated by means of a lever 238 which is non-rotatably secured to the righthand end of the shaft and is provided with a pair of stop pins 238, 248 which project sidewardly so as to lie beneath a felt pad 242 secured to the plate 2I8. The switches are actuated by means of a drawbar 243 which, as shown in Figure 7, is guided for longitudinal movement in a suitable portion of the console and is located where it may be easily actuated by the player. A full stroke plate 244 is pivotally mounted at 248 upon a suitable support 248. A tension spring 258 has one end anchored to the support 248 and its other end secured to a pin 288 carried by the plate 244. The switch lever 238 is connected to the plate 244 by means of a link 252 of adjustable length. The spring 258, being normally eccentric of the pivot 248, is effective to swing the plate 244 in either direction from its dead-center position and thus prevents the shaft 228 from coming to rest in any but its extreme positions Circuit diagram and charts The circuit diagram shown in Figure 9 and the chart, Figures 10 and 10a. together constitute a disclosure of the circuits by means of which the generators may be connected to the output circuit.

In Figure 9 are illustrated some of the generators which may be utilized in sounding the tone Ci. The key for controlling this note is designated C4 in Figure and upon depression is adapted to move an insulating strip 200 downwardly thereby closing switches I82, I, 206. and 280, which are illustrative of any number of switches which it may be found desirable to utilize in a particular construction. The flexible arm of switch 262 is connected through a high impedance element 210 to the output terminal of a transformer 112, the primary of which is connected in a closed series circuit including the winding 200 of the generator and a condenser 214. As more fully disclosed in my aforesaid Patent No. 1,956,850, the impedance elements 210. a plurality of which are connected to the secondaries of each of the transformers 212 are preferably in the form of high resistance wires physically, as well as electrically, connecting the secondary of the transformer with the key control switch. and their impedance values are preferably very high relative to the internal impedance of the generators and relative to the load to which they are adapted to be connected. In this way the impedances I limit the current which may flow to the output circuit through any one of the key control switches and thereby prevent one circuit from "robbing" the others.

The key switch 264 is similarly connected to the secondary of a transformer 212 associated with phonic wheel generators 0i, Bio, and Bib. The windings 200 associated with the phonic wheel generators Ola and Slb are each adapted to be connected in parallel with the winding 200 of the generator Si by means of its associated switch 2i0 which is one of the switches of the gang switch assembly above described.

In a similar manner the key switch arm I" is connected with the phonic wheel generator 88, and may upon closing of the gang switch Ill associated therewith receive current from the phonic wheel 68a and "b, which in this instance, are mounted side by side as shown in Figure lb, and in effect constitute a single generator of two frequencies.

Similarly, the key switch arm 208 is connected to receive current from phonic wheel generator 13, and also from phonic wheel generator 13a, "b when its associated gang switch ii! is closed.

The key switches 262, 284, 288, 260 are adapted to make contact respectively with the bus bars 282, 284, 286, and 288. By means of switches 289 actuated by a preset key 290, (of which a plurality are provided) these bus bars may be selectively connected to any one of a plurality of taps on the primary 292 of the output transformer, the secondary 294 of which is adapted to be connected through suitable output control circuits 200 and output control devices 298 to an amplifier 300 which in turn is connected to a loud speaker 302. The output control devices may constitute suitable volume control means, tremulant controls, tone controls, and the like. In general, the preset quality control switches 289 and the associated circuits. and the remaining portions of the output circuit may be of the type and construction disclosed in my aforesaid Patent No. 1,956,350.

The primaries of the transformers 212, together with their associated windings 200 and condensers I'll each constitutes a fllter circuit which will be effective to attenuate frequencies slightly below that which the associated generator is designed to produce and also, to attenuate frequencies substantially higher than the nominal frequency of the associated generator. In this way, currents of half the nominal frequency of the generator or of lower frequency, as well as a large proportion of the unintended higher harmonics, which might otherwise be supplied by the generator, due to slight unavoidable imperfections in its construction are filtered out, and the current delivered to the output circuit is substantially wholly of the desired frequency or frequencies.

The chart, Figures 10 and 10a, constitutes a complete tabulation of the elements of the chorus generators, the first column I showing the number of the solo generator with which the chorus generators are associated and also indicates the musical note, or the key to which the chorus generators are connected to supply the fundamental partial.

Column 11 gives the reference characters of the brass driving gears used to drive the phonic wheel generators, while column III indicates the numbers of the teeth in these driving gears. Similarly, columns IV and V show respectively the reference characters and numbers of teeth on the driven gears. Column VI indicates the reference characters of the phonic wheels of the various generators, while column VII shows the number of high points or teeth formed in the peripheries of the various phonic wheels.

Column VIII shows the frequencies of the currents generated by the various chorus generators while column IX shows the frequencies generated by the solo generators whose pitch and numbers appear in column 1.

Column X shows the difference in frequencies between the two chorus generators and the associated solo generator. This frequency difference is. of course, given in cycles per second and when the chorus generator is of lower frequency than the solo generator, the difference is shown as negative, while when the chorus generator generates current of frequency higher than that of the solo generator, the difference is indicated as positive.

This chart may be read in the following manner. Reading for example, the first two lines of the tabulation appearing in Figure 10, these lines would be interpreted to mean that the key G4, which controls the note having the tone designated musically as G4, has a fundamental tone produced by a generator number 56; that the chorus generators associated with the generator 58 are driven respectively by driving gears lei and iiiia which have 57 and 91 teeth respectively. The gear iiii drives Bakelite driven gear III which has 92 teeth, while the gear iiila meshes with Bakelite driven gear i2ia which has '74 teeth; the driven gear iii drives the phonic wheel 56a which has 63 high points, while the driven gear liia drives phonic wheel 56b which has 32 high points. The phonic wheels 66a and 58b generate, respectively, currents of frequencies 780.652 and 787.026 respectively, while the frequency generated by the solo generator 56 is 784.000 cycles per second; column X shows that the phonic wheel "a generates a frequency 3.348 cycles per second less than that of the solo generator 66, while the phonic wheel Ilb generates a current 3.026 cycles per second higher than that of the solo generator 58.

By comparison of the figures of column X with the frequencies set forth in column IX, it will be apparent that the frequencies of the chorus generators are in the order of from two to five parts in a thousand greater or less than the frequencies of the corresponding solo generators.

\ Operation The operation of the instrument is substantially the same as that set forth in my aforesaid Patent No. 1,956,350, except that when it is desired to produce the effect of a chorus of instruments as distinguished from the effect of a solo instrument, the player will pull the drawbar 242 outwardly, and thereby simultaneously close all of the switches 2l8, and thus connect the chorus generators in parallel with their associated solo generators. The instrument may then be played and controlled in the usual manner until a solo effect is desired when the drawbar 242 may be pushed inwardly, thereby opening all the switches N8 of the gang switch and disconnecting the chorus generators. With the gang switches Ill open, the instrument will be played and will produce solo tones in the usual manner.

The addition of frequencies generated by the chorus generators, which are slightly above and below the frequencies of the corresponding solo generators adds materially to the richness and fullness of the tone produced, and greatly improves the musical effectiveness of the instrument.

The pre-selector switches by which the tone quality is determined, may, for example, be set for the production of a trumpet tone. Thus, upon closure of the gang switches 2l8, the instrument will produce the effect of a chorus of trumpets. The basic tone quality is the same whether the gang switches 2l8 are closed or open. When the switches are closed there is, however, a decided difference in the general effect of the music. The listener obtains an impression of greater fullness and richness of the tone such as characterizes the difference between orchestral music in which a number of instruments of the same kind are simultaneously played, and a solo rendition by one of such instruments.

When an instrument producing a sustained tone is played in an auditorium or room having sound reflecting walls, it will be found that in certain parts of the room, certain frequencies will be amplified, while other frequencies will be attenuated due to interference of the sound waves. This so-called room pattern effect" is sometimes noticeable when playing the instrument of my invention without the use of the chorus generators. When, however, the instrument is played with the chorus generators connected by closure of the switches 2l8, this effect is slightly less pronounced since even though one particular frequency may be attenuated at a certain point in the room, the other two frequencies of the group will probably be heard in their full degree of loudness. Thus, the simultaneous production of sounds of frequencies differing from each other but very slightly in frequency, to a large extent overcomes the effect of the "room pattern" and materially improves the quality of the music as actually heard.

The chorus generators are preferably adjusted so that the currents product thereby will be of substantially the same power as that of their associated solo generators. In this way, the chorus effect is produced with such fidelity that the listener can ordinarily distinguish but a single.

tone, even though, as a matter of fact, the tone is a composite tone of three sound waves of substantially the same frequency.

Although I have disclosed the chorus generators for production of tones in the higher registers, they may, if desired, be supplied for the lower registers. However, the musical effect of chorus generators in the tones of lower pitch is not as musically desirable as in the higher registers.

While I have shown and described a partlcular embodiment of my invention, it will be apparent to those skilled in the art that the fundamental features thereof may be embodied in various other forms, all coming within the scope of my invention. I therefore, do not wish to be limited to the specific details as set forth herein, but desire to include within the scope of the accompanying claims all of such equivalent constructions as may be usable to accomplish substantially the same results in substantially the same way.

I claim:

1. In an electrical musical instrument, the combination of a set of solo generators of currents having the frequencies of the tones of the tempered musical scale, and plurality of chorus generators arranged to be connected respectively in parallel with said generators, and generating currents of frequencies differing from those generated by their associated solo generators by an amount in the order of 0.4%. and means for connecting said chorus generators in parallel with their respective solo generators.

2. In an electrical musical instrument, the combination of a plurality of electrical generators for producing electrical pulsations of frequencies differing from each other by an amount in the order of four parts in a thousand, means for translating said electrical pulsations into sound. and common means for connecting said generators to said translating means.

3. In an electrical musical instrument, the combination of a plurality of solo electrical generators of currents having the frequencies respectively of the tones of the tempered musical scale, a plurality of auxiliary electrical generators connected respectively in parallel with said solo generators, each of said auxiliary generators producing a current of a frequency differing from that generated by its associated solo generator by an amount less than 0.6%.

4, In an electrical musical instrument, the combination of a set of solo electrical generators, means for translating electrical currents from said generators into sound, a plurality of chorus electrical generators, at least one associated with each of said solo generators of said set, and means for connecting said chorus generators in circuit with said solo generators, whereby the sound produced by said translating means as generated by one of said solo generators and its associated chorus generator, will produce the effect of a plurality of musical instruments playing the same note.

5. In an electrical musical instrument, the combination of a first set of generators of electrical impulses at the frequencies of the tempered scale, and a second set of generators of'electrical impulses at frequencies respectively greater than those of said first set by amounts of the order of 0.4%.

6. In an electrical musical instrument, the combination of a first set of generators of electtical impulses at the frequencies of the tempered musical scale, a second set of generators of electrical impulses at frequencies diiiering from those a of said first set by amounts in the order of 0.4%, means for translating said impulses into sound, and means for selectively connecting said generators to said translating means.

I. In an electrical musical instrument, the com- ;o bination of a first set of generators of electrical impulses at the frequencies of the tempered musical scale, a second set of generators of electrical impulses at frequencies greater than those of the iirst set by an amount in the order 0.4%. and a s third set of generators of impulses of frequencies less than those of said first set by an amount in the order of 0.4%, and means for translating electrical impulses received from said sets of generators into sound. 4

8. In an electrical musical instrument, the combination of a set of primary generators, a set of secondary generators associated respectively with said primary generators, electro-acoustical translating means, means for rare-determining the relgs ative effective intensities of impulses received by said translating means irom said generators for supplying the different partials of a musical tone, and means for connecting said secondary generators in parallel with their associated primary so generators respectively, without disturbing the eflectiveness of said intensity rare-determining means.

0. In an electrical musical instrument, the coma,1so,sos

bination of a set of primary generators for generating the frequencies of the tempered musical scale, a set of secondary generators for generating frequencies differing respectively from those produced by said primary generators by an amount in the order of 0.4%, eiectro-acoustical translating means, means for selectively connecting said primary generators to said'translating means,.and selectively operable means to connect said secondary generators respectively in circuit with their associated primary generators.

10. In an electrical musical instrument, the combination of a plurality of solo generators of the frequencies of the tempered musical scale, chorus generators associated respectively with said solo generators for generating frequencies difl'ering slightly from those generated by the solo generators, electro-acoustical translating means, means for selectively connecting said solo generators and their associated chorus generators to said translating means, and optionally operable means for rendering said chorus generators ineflective.

ii. In an electrical musical instrument, the combination of a plurality of solo generators, chorus generators associated respectively with said solo generators for generating frequencies differing slightly from those generated by the solo generators, and means for connecting said chorus generators in circuit with their respective solo generators.

LAURENB HAMMOND. 

